Satellite system optimization by differentiating application of adaptive coding and modulation

ABSTRACT

Systems and methods for differentiated application of an Adaptive Coding and Modulation (ACM) to enhance link performance in satellite communication systems are disclosed. A system may include a processor and a memory storing instructions, which when executed by the processor, cause the processor to dynamically compute bandwidth capacity of a terminal from a plurality of terminals. Based on the computed bandwidth capacity of the terminal, the processor may automatically determine a ModCod to be applied for transmission to or from the terminal to optimize bit error rate (BER) performance. The to processor may determine the ModCod using an ACM technique. For the plurality of terminals, the processor may dynamically determine aggregate bandwidth availability and congestion within the ACM technique to optimize sharing of available bandwidth.

TECHNICAL FIELD

This patent application is directed to satellite communication systemsand, more specifically, to systems and methods for differentiatedapplication of Adaptive Coding and Modulation (ACM) to enhance linkperformance in satellite communication systems.

BACKGROUND

Adaptive Coding and Modulation (ACM) is a technique for optimizingperformance of a link channel for satellite systems, by using anefficient modulation and Forward Error Correction (FEC) code combination(ModCod) for each terminal. However, link channels pertaining tomultiple terminals may be associated with varying link conditions due tostatic and/or dynamic factors such as, for example, sizing/configurationof equipment, traffic congestion, weather, and other such factors. Forexample, transmission to one terminal may be subject to relatively worselink conditions than another terminal. Conventional ACM implementationmay not consider these factors, thus leading to poor link quality orunoptimized bit error rate (BER) performance for such terminals.

In addition, the conventional ACM implementation may treat the terminalsindependently of each other. This may also lead to inefficient usage ofbandwidth capacity of each link channel, especially in case of linkchannels with relatively lesser traffic. Further, the traditional ACMtechnique may not consider aspects such as variable demand andaffordability of service, thus lacking customized service levels basedon requirements of an end user. Furthermore, even for a particularterminal, the link transmission may need varying level of robustness orspectral efficiency of the transmission depending on type/class oftraffic. Additionally, the conventional implementation may also lackprovisions for an opportunistic downgrade of forward/return link to amore robust ModCod in case of available capacity, thus leading toinefficient ACM technique.

BRIEF DESCRIPTION OF DRAWINGS

Features of the systems and methods are illustrated by way of exampleand not limited in the following Figure(s), in which like numeralsindicate like elements, in which:

FIG. 1A illustrates a system for differentiating application of ACM toenhance link performance in satellite communication systems, accordingto an example;

FIG. 1B illustrates a typical/conventional system for implementing ACM;

FIG. 2 illustrates system elements/interactions pertaining todifferentiating ACM implementation by system of FIGS. 1A-1B, accordingto an example;

FIG. 3 illustrates a method for differentiating application of ACM toenhance link performance in satellite communication systems, accordingto an example;

FIG. 4 illustrates an example of a partially configured trajectory tablepertaining to ACM forward link, according to an example;

FIG. 5 illustrates a block diagram showing downgrade in terminal ModCodon a shared forward channel, according to an example;

FIG. 6 illustrates an example of a configured trajectory table for areturn link path of a terminal, according to an example;

FIG. 7 illustrates a block diagram of ModCod downgrade for anuncongested forward channel, according to an example; and

FIG. 8 illustrates a block diagram of a computer system fordifferentiating application of ACM to enhance link performance,according to an example.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the present systems andmethods are described by referring mainly to examples and embodimentsthereof. In the following description, numerous specific details are setforth in order to provide a thorough understanding of the systems andmethods described herein. It will be readily apparent, however, that thesystems and methods may be practiced without limitation to thesespecific details. In other instances, some methods and structuresreadily understood by one of ordinary skill in the art have not beendescribed in detail so as not to unnecessarily obscure the systems andmethods described herein. As used herein, the terms “a” and “an” areintended to denote at least one of a particular element, the term“includes” means includes but not limited to, the term “including” meansincluding but not limited to, and the term “based on” means based atleast in part on.

As described above, Adaptive Coding and Modulation (ACM) may be used tooptimize link performance for terminals, by using most efficientmodulation and forward error correction (FEC) code combination(hereinafter also referred to as “ModCod”) for each user terminal. Themodulation and FEC code combination may be implemented in the form ofModCod, which may achieve a target link quality at pre-defined linkconditions. The link conditions pertaining to any of the forward link orthe return link may be affected by static and/or dynamic factors. Forexample, the static factors may include, for example, sizing andperformance of gateway device, terminal device and/or terminal, andother pre-defined static factors. The dynamic factors may include, forexample, weather attenuation or interference on uplink and/or downlinkand other variable factors. Further, out of a plurality of terminals,each terminal may have variable dynamic factors that may lead tovariable transmission, even in case of similar ACM implementation. Forexample, transmission to one terminal may be subject to relatively worseweather conditions than another terminal, thus requiring variableimplementation of ACM. This implementation of ACM may compensate forvariable conditions (or dynamic factors) with more robust modulationand/or coding during transmission.

The systems and methods may also utilize the ACM to maximize thecapacity efficiency for bandwidth used by each given user terminal,while optimizing target bit error rate (BER) performance for theparticular user terminal. The term BER may pertain to number of biterrors per unit time. The BER may be in uniformity with satellite linkconditions (such as weather attenuation) affecting the particular userterminal. The present technique may implement ACM in a manner todetermine specific ModCod to be used for transmission to and/or from theparticular user terminal to optimize the BER performance. The systemsand methods described herein may consider the fact that implementationof highly robust ModCods may utilize bandwidth at lower bits per symbol(bps) efficiency than do less robust ModCods. Therefore, the terminalsusing robust ModCods (highly robust) may consume more shared systemcapacity than terminals using more spectrally efficient ModCods (lessrobust), to convey same amount of end user traffic. Thus, unlikeconventional ACM, the systems and methods described herein, recognizesthat each link/traffic may not be equivalent. Therefore, the system candifferentiate one terminal from a second terminal based on any or acombination of aspects, such as for example, congestion parameters, oravailability of a service level defined for the respective terminals.

Specifically, the systems and methods described herein, may also enabledifferentiating ACM treatment either between terminals, or betweendifferent traffic classes within given terminals. This may be performedin one or more ways. In some examples, the system may enable todynamically determine aggregate bandwidth availability and congestionwithin the ACM technique to optimize sharing of available bandwidth fora plurality of terminals. The systems and methods described herein, mayalso facilitate opportunistic downgrade to a more robust forward ModCodand/or return ModCod when capacity is available, to minimize BER. Insome examples, the systems and methods described herein, may recognizethat ACM can be adjusted opportunistically for certain traffic classesduring periods of low system congestion or when bandwidth is otherwiseavailable. In some examples, systems and methods described herein, mayfacilitate adaptive use of different ACM trajectory tables at a givensite, based on various system metrics and controls. Furthermore, for anoptimized BER performance, the systems and methods described herein mayfacilitate automatic manipulation of forward control traffic ModCodbased on utilization or efficiency thresholds, and other such aspects.Several other crucial aspects will be described in detail herein.

As described herein, the term “link condition” may refer to a set ofstatic and/or dynamic factors that may affect integrity of signalstransmitted to and/or from a terminal. The term “link quality” may referto an error metric for the link. For example, “link quality” may bereferred to in terms of average uncoded BER or average packet error rate(PER). In another example, the term “link quality” may also becorrelated to a link quality metric that can be measured by a receiver,such as signal-to-noise ratio (SNR) and other such metrics. The usage ofterms such as “more efficient ModCod” may refer to delivery of higherunits of uncoded bits/symbol. In this usage, the term “more efficient”may be used interchangeably with the term “less robust”. The use of theterms “more robust ModCod” may refer to delivery of an increased codeprotection per uncoded bit. Similarly, the term “less efficient” may beused interchangeably with the term “more robust”. Additionally, the term“higher ModCod” may be used herein to refer to a more efficient ModCod,and the term “lower ModCod” may be used here to refer to a lessefficient ModCod.

FIG. 1A illustrates a system 100-1 for differentiating application ofACM to enhance link performance in satellite communication systems,according to an example. In some examples, the system 100-1 may depict asatellite communication system capable of providing at least voiceand/or data services. In some examples, the satellite communication maybe a transponded satellite that relays a shared forward channeltransmission signal from a gateway 130 to at least one terminal 110. Thesystem 100-1 may include any number of terminals 110, a satellite 120,the gateway 130, a network data center 140, a network management system(NMS) 150, a business system 160, or other various system elements orcomponents. The system 100-1 may also include a private network 170and/or public network 180. It should be appreciated that the system100-1 depicted in FIG. 1A may be an example. Thus, the system 100-1 mayor may not include additional features and some of the featuresdescribed herein may be removed and/or modified without departing fromthe scopes of the system 100-1 outlined herein.

The terminals 110 may be any variety of terminals. For example, theterminals 110 may be customer terminals, such as very small apertureterminals (VSATs). It should be appreciated that VSATs may be terminalsthat are mounted on a structure, habitat, or other object or location.Depending on application, the terminals 110 may include or incorporateany number of antenna dishes, which may be provided in various sizes,depths, or dimensions (e.g., small, medium, large, etc.). Although theterminals 110 may typically remain in the same location once mounted,the terminals 110 may be removed from their mounts, relocated to anotherlocation, and/or may be configured to be mobile terminals. For instance,the terminals 110 may be mounted on mobile platforms that facilitatetransportation thereof from one location to another. Such mobileplatforms may include, for example, any number of mobile vehicles, suchas cars, buses, boats, planes, etc. It should be appreciated that suchterminals 110 may generally be operational when still and not whilebeing transported. That said, there may be scenarios where the terminals110 may be transportable (mobile) terminals that remain operationalduring transit. As used herein, the terms “terminal,” “customerterminal,” “satellite terminal,” and/or “VSAT” may be usedinterchangeably to refer to these terminal types.

It should be appreciated that any number of customer premise equipment(CPE) (not shown) may be communicatively coupled to the terminals 110.In some examples, the customer premise equipment (CPE) may include anynumber of computing or mobile devices. For example, such a computing ormobile device may include a laptop, a tablet, a mobile phone, anappliance, a camera, a sensor, a thermostat, a vehicle, a display, etc.In general, the customer premise equipment (CPE) may include, withoutlimitation, any number of network-enabled computing devices, elements,or systems. It should be appreciated that a network of such devices maybe commonly referred to as the “Internet of Things” (I).

As shown in FIG. 1A, there may be different types of terminals or aplurality of groups of terminals 110 (e.g., customer VSATs). Forexample, each terminal such as 110A, 1106 (collectively referred to asterminal or terminals 100) may be pertain to an individual terminal orplurality of groups. In some examples, the terminal 110A may beterminal(s) that involve relatively better conditions than theterminal(s) 1106. For example, weather conditions may be relativelybetter in transmission to and/or from the terminals in case ofterminal(s) 110A than terminal(s) 1106. The satellite 120 may be anobject intentionally placed into orbit. In some examples, the satellite120 may be an artificial satellite that is configured to transmit andreceive data signals. For example, the satellite 120 may form one ormore beams and provide connectivity between at least the terminals 110and the gateway 130. More specifically, the satellite 120 maycommunicate data signals using these beams with the terminals 110 via aterminal return channel 115 and a terminal forward channel 105, and withthe gateway 130 via a gateway return channel 145 and a gateway forwardchannel 125. It should be appreciated that the satellite 120 may formany number of beams and channels to communicate data signals with anynumber of components, even beyond the terminals 110 or the gateway 130as shown.

In some examples, the satellite 120 may be a communication satellite,which may be in geosynchronous (GEO) orbit, low earth orbit (LEO) or midearth orbit (MEO) satellite. The link conditions may vary more rapidlyfor LEO and MEO systems as the propagation path may be longer or shorterdepending on the satellite location and different atmospheric/weatherconditions encountered.

In some examples, the satellite 120 may include, but not limited to, atransponded satellite, a regenerative satellite, and/or other similarsatellite that implement ACM for forward and/return signal carriers. Incase of regenerative satellite, ACM adaptive controls applicable to thegateway 130 might may instead be performed by the satellite 120, ormight be performed by the satellite 120 under control of the gateway 130or some other ground system. Furthermore, in some examples, thesatellite 120 may operate in geosynchronous, mid-earth, low-earth,elliptical, or some other orbital configuration.

The gateway 130 may include or be communicatively coupled to atransceiver 135, such as a radio frequency transceiver (RFT). Thetransceiver 135 may include an antenna unit of any type (e.g.,transmitter, receiver, communication element, etc.), which may transmitand receive signals. In some examples, the transceiver 135 may beuseable, by the gateway 130 of system 100, to transmit and receive datafrom the terminals 110, via communications from the satellite 120, andmay be configured to route data and traffic from these terminals 110 toany other element or component in the system 100, such as the networkdata center 140 and/or network management system (NMS) 150. The gateway130 may be further configured to route traffic to/from the publicinternet 180 and/or private network 170 across the satellitecommunication channels 115, 105, 125, or 145 to/from any terminal 110,which would then provide data communications or route traffic to/fromany customer premise equipment (CPE) (not shown) associated with theterminal 110. Although depicted as a single element, the gateway 130 mayinclude a single gateway, multiple gateways residing locally orremotely, in full or in part, relative to the other system components.As described in more detail below, the gateway 130, the network datacenter 140, and/or the network management system (NMS) 150 may provideoperations associated with the system for determination of ModCod indifferentiating ACM application.

The system may include a processor (e.g., a computer processing unit(CPU), etc.), a data store and other such elements. In some examples,the system may be implemented in the gateway 130. The processor mayinclude also various configurations including, without limitations, apersonal computer, laptop, server, and other elements. The data storemay be used, for example, to store and provide access to informationpertaining to various operations of and in the system 100-1 or 100-2.Although depicted as a single element, the processor and/or the datastore may be configured as a single element, multiple elements, or anarray of elements. For example, the gateway 130 may include any numberof processors and/or data stores in order to accommodate the needs of aparticular system implementation. Various examples may further providefor redundant paths for components of the gateway 130. These redundantpaths may be associated with backup components capable of beingseamlessly or quickly switched in the event of a failure or criticalfault of any primary component.

Referring to FIG. 1A, the network data center 140 may be communicativelycoupled to the gateway 130, as well as other system components, such asthe network management system (NMS) 150, private network 170, and/orpublic network 180. In some examples, the network data center 140 may bea satellite network data center that is configured to perform ACM basedfunctions. In some examples, the network data center 140 may include aplurality of network data centers that are local or remote, in full orin part, relative to the other system components.

The network management system (NMS) 150, maintains, in full or in part,various information (configuration, processing, management, etc.) forthe gateway 130, and terminals 110 and beams supported by the gateway130. It should be appreciated that the network management system (NMS)150 may or may not be co-located within the same physical structure asthe gateway 130. Furthermore, the network management system (NMS) 150may be single or a plurality distributed components that may becommunicatively coupled to each other and/or with other system elements,such as the gateway 130 (e.g., using the previously described hardwareand external networks). The network management system (NMS) 150 may,among other things, include a configuration manager or other similarmanagement unit.

The business system 160, or other various system elements or components,may also be communicatively coupled to the network management system(NMS) 150 and/or gateway 130. In some examples, the business system 160may include a virtual network operator (VNO), which may be configured tocommunicate with the gateway 130 and/or the network management system(NMS) 150 in order to perform the differentiated application of ACM toenhance link performance. More particularly, a virtual network operator(VNO), in some scenarios, may be a business or government entity, thatmay have access (by purchase or license) to a managed service andassociated capacity from a satellite network operator in order toprovide communication connectivity and/or communication for aprivately-owned set of terminals 110. The virtual network operator (VNO)may therefore manage various aspects of such terminals 110 via thegateway 130 and/or the network management system (NMS) 150.

The private network 170 and/or public network 180 may include anyvariety of networks. For example, the private network 170 may be a localarea network (LAN), and the public network 180 may be a wide areanetwork (WAN). That said, the private network 170 and/or public network180 may each also be a local area network (LAN), wide area network(WAN), the Internet, a cellular network, a cable network, a satellitenetwork, or other network that facilitates communication between thecomponents of system 100-1 as well as any external element or systemconnected to the private network 170 and/or public network 180. Theprivate network 170 and/or public network 180 may further include one,or any number, of the exemplary types of networks mentioned aboveoperating as a stand-alone network or in cooperation with each other.For example, the private network 170 and/or public network 180 mayutilize one or more protocols of one or more clients or servers to whichthey are communicatively coupled. The private network 170 and/or publicnetwork 180 may facilitate transmission of data according to atransmission protocol of any of the devices and/or systems in theprivate network 170 and/or public network 180. Although each of theprivate network 170 and/or public network 180 is depicted as a singlenetwork in FIG. 1 , it should be appreciated that in some examples, eachof the private network 170 and/or public network 180 may include aplurality of interconnected networks as well.

FIG. 1B illustrates a typical/conventional system 100-2 for implementingACM. As shown, FIG. 1B is provided to exemplify variableconditions/parameters pertaining transmission to and/or from theterminals 110A, 110B that may be required to be considered to optimizeBER performance. As depicted in FIG. 1B, in a conventional ACMimplementation, the satellite 120 may relay a forward channeltransmission signal F (125, 105 a, 105 b) from the gateway 130 toterminals 110A and 110B. The forward channel F may include uplink signalpath 125 from gateway 130 to the satellite 120, and downlink signalpaths 105 a and 105 b from the satellite 120 to terminals 110A and 110Brespectively. The path of the forward channel may be based onconnectivity and/or translation of the uplink signal path and thedownlink signal paths. The terminals 110A and 110B also include returnsignal paths i.e. TR1 and TR2 respectively that are transmitted throughsatellite 120 to the gateway 130. The terminal 110A may transmit returnchannel T1R via uplink path 115 a to the satellite 120, which mighttranspond this signal into downlink path 145 a. The terminal 110B maytransmit return channel T2R via uplink path 115 b to the satellite 120,which might transpond this signal into downlink path 145 b. As depictedin FIG. 1B, terminals 110A and 110B may be positioned at differentlocations that are subject to varying weather conditions andinterference in their respective downlink paths (105 a and 105 b) and/oruplink paths (115 a and 115 b) from and/or to the satellite 120. Forexample, the downlink path 105 b may be subjected to cloudy weatherconditions than 105 a, and/or the uplink path 115 b may be subjected tocloudy weather conditions than 115 a. This may cause difference inquality of downlink and/or uplink signal paths for the respective sharedforward channel F and/or return channel (TR1/TR2). One of the majorlimitations of conventional ACM is that the terminals are treatedindependently, irrespective of the corresponding link conditions.

The system and method described herein (in FIG. 1A), effectivelyaddresses these issues based on differentiated application of ACM. Thesystem of FIG. 1A may include a memory operatively coupled with aprocessor. Upon execution of a set of instructions, the processor maydynamically compute bandwidth capacity of a terminal for the pluralityof terminals. Based on the computed bandwidth capacity of the terminaland using ACM technique, the processor may automatically determine aModulation and Coding combination (ModCod). The ModCod may be appliedfor transmission to and/or from the terminal, which may optimize biterror rate (BER) performance. In some examples, the system may be adynamic link adaptation system. In some examples, the system may beimplemented in the gateway 130 (or a gateway device).

Referring back to FIG. 1A, for the plurality of terminals 110 (orplurality of terminals), system or processor may dynamically determineaggregate bandwidth availability and congestion within the ACM techniqueto optimize sharing of available bandwidth. For example, the forwardchannel transmission signal F may be a forward shared carrier that maycarry/transmit data to be received by multiple terminals 110. This is asignificant improvement over conventional ACM implementation that maytreat the terminals independently, which may lead to wastage inbandwidth capacity usage.

In some examples, using the system and method described herein, the ACMtechnique may use a trajectory table to adaptively change and/or allowpermission for use of the applied ModCod by the terminal. Theconfiguration of the trajectory table may be altered based on capacityutilization and expected congestion during the day. In some examples,the trajectory table may authorize use of a given ModCod format for adefined traffic class of service for the terminal. Various other aspectspertaining to the trajectory table will be clear in light of examplesdiscussed herein. In some examples, using the system and methoddescribed herein, the applied ModCod may be changed based on monitoringand periodic comparison of shared forward channel aggregate utilizationwith a pre-defined threshold. The change may include downgrading theModCod when the shared forward channel aggregate utilization is lessthan the pre-defined threshold. In other words, “downgrading” the modModCod may refer to less efficient functionality, so in this example, ifthe forward channel is empty, the terminal might be authorized to use aless efficient ModCod, but when the forward channel is congested theterminal might not be permitted to use such a ModCod.

In an example embodiment, using the system and method described herein,applied ModCod may be changed for the terminal based on any or acombination of parameters associated with at least one of satellitelink, congestion, weather, availability of a service level to beprovided to the terminal, terminal radio power, or antenna size. Theparameters may pertain to various static and/or dynamic factors that maylead to differential parameters for terminals 110A and 1106. Forexample, the forward channel transmission signal F for terminal 110A (or1106) may be affected by static/constant factors such as, for example,sizing and performance of the gateway 130, terminal 110A (or 1106)and/or satellite 120. Further, as shown in FIG. 1B, the forward channeltransmission signal F for terminal 110A (or 110B) may be affected bydynamic factors such as weather attenuation, interference on uplinksignal path 125 and/or interference on downlink signal path (105 a, 105b). Similarly, the return channel TR1 and/or TR2 for terminal 110A (or110B) may be affected by static/constant factors such as, for example,sizing and performance of the gateway 130, terminal 110A (or 110B)and/or satellite 120. Further, as shown in FIG. 1B, the return channelTR1 and/or TR2 for terminal 110A (or 110B) may be affected by dynamicfactors such as weather attenuation, interference on uplink signal path(115 a, 115 b) and/or interference on downlink signal path (145 a, 145b). As depicted in FIG. 1B, the return uplink path 115 b of terminal110B may be subjected to different weather conditions (cloudy weather)than the return uplink path 115 a of terminal 110A.

To address this, the system and method described herein may enable toapply a differentiating ACM in such a way that the applied ModCod may bechanged for the terminal 110B to compensate for varying conditions withmore robust modulation and/or coding to ensure the transmitted data fromterminal 110B is received correctly by the gateway 130. In someexamples, one terminal may be differentiated from a second terminalbased on any or a combination of congestion parameters, and availabilityof a service level defined for the respective terminals. In someexample, the differentiating ACM may be implemented by applied ModCod,such that through ACM the gateway 130 may be enabled to optimizerespective forward transmission carrier F individually for each of themultiple terminals 110 receiving the shared carrier. The resultantwaveform may be designed to include successive codeblocks. In anexample, each codeblock may be modulated and coded to optimize linkquality to adapt to the link conditions of respective terminals to whichdata in that codeblock is addressed. The return channels T1R and T2Reach carry return traffic for each respective terminal 110A and 110Brespectively, and ACM optimization of transmission for the return linksmay consider link conditions of the respective terminal. In an example,the forward link transmission F or return link transmission (TR1, TR2),successive codeblocks or transmissions may be modulated and/or codeddifferently, to be optimized for terminals experiencing different orchanging link conditions. For example, for forward link transmission toa respective terminal (110A or 110B), corresponding codeblockscontaining broadcast or multicast data may be sent using a ModCod thatis sufficiently robust for the link conditions applicable to therespective terminals. In another example, forward codeblocks containingsystem control messages destined to all terminals 110 (includingterminals for which link conditions are unknown to the gateway 130) maybe sent using a relatively more robust ModCod. It should be appreciatedthat the mentioned examples may be applicable to the adaptive waveformdefined by standard pertaining to digital video broadcasting—satellitesecond generation (DVB-S2), but may also be applicable to other forwardand return path waveforms with adaptive properties, in any case of beingstandardized or proprietary. The examples disclosed herein may pertainto multiple aspects of ACM optimization. For example, the ACMoptimization may be applied independently or in combination for a givenchannel used by the terminals 110, wherein the terminal 110 might beassociated with a single forward channel, or different forward channelsover time. Similarly, a terminal may use a single return channel, ormight use different return channels over time, and ACM optimization maybe applied to independently adapt to conditions of each link while inuse. In some examples, specific classes of terminals may simultaneouslyreceive multiple forward channels from the same or different satellites,and might simultaneously transmit multiple return channels to the sameor different satellites.

FIG. 2 illustrates system elements/interactions pertaining todifferentiating ACM implementation (corresponding to FIG. 1A), accordingto an example. As per an example described in FIG. 2 , terminal 110A mayreceive shared forward channel 125 from gateway 130 that is relayed viasatellite 120 (through 105 a). The shared forward channel 125 mayforward the transmission/data from the satellite 120 to the terminal110A (through 105 a), which is received by an antenna 202. The terminal110A may include various modules to extract and/process the receivedtransmission data, control signaling addressed to the terminal and/orvarious other functions. In an example, the received data may beforwarded to a protocol processing module 206, and further sent to anappropriate user device 210 and/or with external user devices (208-1,208-2, and other user devices). If applicable, the received data may besubjected to decoding at receiving module 204, prior to sending to theprotocol processing module 206. In an example, the protocol processingmodule 206 may perform optimizing functions. The protocol processingmodule 206 of terminal 110A may receive data from the user device 210via local area network (LAN) or wireless LAN (WLAN) interface. Thereceived user data may be queued for transmission to the satellite 120by the return transmit module 212. The terminal 110A may transmit thereceived user data and/or control signaling on a return channel 115 athat is relayed via satellite 120 to the gateway 130, as shown in FIG. 2. In an example, the gateway 120 may receive the transmitted data fromsatellite 120 via the radiofrequency (RF) terminal 254. The gateway 130may extract/process the user data, using a gateway protocol processingmodule 252, and may forward the user data to external networks,performing protocol processing functions and/or optimizing as required.

In an example and as depicted in FIG. 2 , the terminal 110A may controloperation/implementation of ACM for forward link 105 a and/or returnlink 115 a. The receiving module 204 of the terminal 110A may measurequality of the forward link signal 105 a, and may provide metrics forthe signal quality to an ACM control module 214. The ACM control module214 may perform averaging/hysteresis processing based on pre-defined(previous measurements) and current metrics to filter out transienteffects. In an example, configured trajectory table 216 may be used byACM technique to adaptively change and/or allow permission for use ofthe applied ModCod by the terminal 110A. Thus, the ACM control module214 may use the configured trajectory table 216 to determine the appliedModCod (forward ModCod/ACM settings) that should be implemented by thegateway 130 for sending data to the terminal 110A. The ACM controlmodule 214 may store the ACM settings at storage 218 and may relay thisinformation pertaining to the forward ModCod (ACM settings) to thegateway 130 through the return transmit module 212. For example, theinformation pertaining to the forward ModCod may be relayed, forexample, in the form of piggybacked on data packets or in the form ofdedicated message(s). The RF terminal 254 of the gateway 130 may receiveand share the received information pertaining to the forward ModCod,which may be relayed to the receiving module 256 and further to thegateway protocol processing module 252. The gateway protocol processingmodule 252 may store the information and/or the corresponding ACMsettings pertaining to terminal 110A in ACM settings storage 258. In thenext phase, the gateway protocol processing module 252 sends a forwarduser data to gateway forward transmit module 260, wherein the module 252indicates the ModCod to be used based on the saved ACM settings forterminal 110A. The gateway forward transmit module 260 may encode theforward user data in codeblocks using the indicated ACM/ModCod settings.This may enable a closed loop for forward ACM under supervision of theACM control module 214 of the terminal 110A, wherein the ACM controlsettings may be consistent with the configured trajectory table 216. Itshould be appreciated that the ACM control module 214 may not benecessarily be present in the terminal 110A but may be alternativelyconfigured in the gateway 130. In an example, the terminal 110A mayrelay metrics for the signal quality of the forward link to the gateway130 that may use a local forward link trajectory table to decide theappropriate forward ModCod for terminal 110A. In an alternate example,the gateway may include a forward receiving module that may maintain ACMsettings for each terminal, rather than the gateway protocol processingmodule 252. The gateway my also include a bandwidth manager 262 tocheck/manage the bandwidth capacity. It should be appreciated that thebandwidth manager 262 may have a number of different functions. In someexamples, the bandwidth manager 262 may monitor aggregate utilization offorward capacity and inform the protocol processing module 252 of therate at which data can be supplied to the forward transmit module 260without overrunning that module (either in an absolute value or with aspeed up/slow down control). In some examples, the bandwidth manager 262may also monitor utilization of that capacity by different virtualnetwork operators and indicate, based on how much capacity they havepaid for, how much traffic the protocol processing module 252 ispermitted to supply for each. In other words, the bandwidth manager 262may provide controls whether certain classes of terminals, or terminalswith certain service plan subscriptions, or certain priorities oftraffic destined to those terminals, are permitted to use certaininefficient ModCods based on current aggregate forward capacityutilization. Several other configurations for deriving/implementing theACM settings may be possible. It may also be appreciated that the abovedescribed implementation may also be applied to return link of theterminal 110A. In that case, the ACM control module 214 may alsodetermine a transmit power level adjustment, based on processed returnlink signal quality metrics, and may determine to make a poweradjustment in addition to or in lieu of a ModCod adjustment. Thisprovides for closed loop ACM operation on the return link, undersupervision of the ACM control module 214, and as per the configuredtrajectory table 216. In this example, the ACM control may be applicablewhen a return channel is a dedicated channel operating a waveform suchas DVB-S2, or is a shared time division multiple access (TDMA) channelwith dedicated time slot allocations.

While the processors, components, elements, systems, subsystems, and/orother computing devices may be shown as single components or elements,one of ordinary skill in the art would recognize that these singlecomponents or elements may represent multiple components or elements,and that these components or elements may be connected via one or morenetworks. Also, middleware (not shown) may be included with any of theelements or components described herein. The middleware may includesoftware hosted by one or more servers. Furthermore, it should beappreciated that some of the middleware or servers may or may not beneeded to achieve functionality. Other types of servers, middleware,systems, platforms, and applications not shown may also be provided atthe front-end or back-end to facilitate the features and functionalitiesof the system 100-1, system component 200, and their components, asshown in FIGS. 1A and 2 .

FIG. 3 illustrates a method for differentiating application of ACM toenhance link performance in satellite communication systems, accordingto an example. The method 300 is provided by way of example, as theremay be a variety of ways to carry out the method described herein.Although the method 300 is primarily described as being performed by thesystem 100-1 of FIG. 1A and/or the system component 200 of FIG. 2 , themethod 300 may be executed or otherwise performed by one or moreprocessing components of another system or a combination of systems.Each block shown in FIG. 3 may further represent one or more processes,methods, or subroutines, and one or more of the blocks may includemachine readable instructions stored on a non-transitory computerreadable medium and executed by a processor or other type of processingcircuit to perform one or more operations described herein. The system100-1 or system component 200, for example, may assess the need fordifferentiating application of ACM based on requirement such as based ona request from terminals or in predetermined regular intervals duringnormal system operations. In some examples, this may be an automatedsequence of actions, as described below and shown in FIG. 3 .

At 310, a bandwidth capacity of a terminal may be dynamically computed.In an example, the bandwidth capacity may be computed at a networkdevice, such as, for example a gateway. At 320, ModCod that needs to beapplied for transmission to and/or from the terminal may beautomatically determined based on the computed bandwidth capacity of theterminal and using the ACM technique. The applied ModCod may optimizebit error rate (BER) performance. In an example, the ModCod may bedetermined at the network device. In some examples, the network devicemay dynamically determine aggregate bandwidth availability andcongestion within the ACM technique to optimize sharing of availablebandwidth for the plurality of terminals. The ACM technique may use atrajectory table to adaptively change and/or allow permission for use ofthe applied ModCod by the terminal.

Although the method 300 may be continuous or automatic, it should beappreciated that the method 300 may be suspended at any time, based onoperator command or automatically by the NMS 150 during certainextraordinary operations, such as major maintenance or upgrade activityor for other reasons. Details for each of these actions will not bedescribed in greater detail below.

In an example, the trajectory table may enable to identify configurationparameters that control selection of applied ModCod (ACM ModCod) basedon processed forward and/or return link signal quality metrics. In someexamples, the configuration of the trajectory table may be altered basedon capacity utilization and expected congestion during the day. FIG. 4illustrates an example of a configured trajectory table 400 pertainingto partial ACM forward link, according to an example. It should beappreciated that the configured trajectory table 400 may be subset oftrajectory table entries, wherein a complete trajectory table mayinclude sufficient ModCod steps to dynamically optimize link quality andthroughput, through ModCod entries. The ModCod entries may includeadditional modulation and coding combinations in between the entriesshown in FIG. 4 . In an example, the configured trajectory table 400 mayinclude a ModCod reference number 402. The ModCod reference number 402may be relayed from terminal 110 to inform gateway 130 and may pertainto type of ModCod that should be used for forward data and controlsignaling sent to the terminal. The configured trajectory table 400 mayalso include a ModCod format 404 indicating the modulation and coding tobe applied for a given reference number. Further, the configuredtrajectory table 400 may include a ModCod entry threshold 406,indicating a first signal quality metric value that should be reached orexceeded for the terminal 110 to consider a given ModCod as eligible foroperation. In an example, the signal quality metric value may includesignal to noise ratio (SNR) or other such metrics, such as bit errorrate (BER). Further, the configured trajectory table 400 may include aModCod exit threshold 408, indicating a second signal quality metricvalue at which terminal 110 may no longer consider the given ModCod aseligible for operation. Based on the configured trajectory table 400,the ACM control module of the terminal (such as 214 in FIG. 2 ) mayselect the most efficient ModCod for the forward path for which theterminal meets the entry threshold. For example, for the entries shownin FIG. 4 , a terminal with a signal quality metric value of 5.0 mayqualify to use ModCod 6 (QPSK ⅔), ModCod 4 (QPSK ½) and ModCod 1 (QPSK¼), but may not qualify for using ModCod 9 (QPSK ⅚), ModCod 12 (8 PSK ⅗)or ModCod 18 (16apsk ⅔), or any other ModCod not shown with entrythreshold value greater than 5.0. In this case, the most efficientModCod may be ModCod 6, providing for QPSK modulation (2 bits persymbol) and ⅔ FEC (2 data bits for every 3 coded bits), giving 4/3 databits per symbol. In some examples, the trajectory table 400 may beordered/customized by increasing efficiency to simplify selectionalgorithm/technique. The range between entry threshold and exitthreshold may be used to overcome toggling between ModCods when signalquality may be near a threshold. In an example, when signal qualitymetric may drop below the entry threshold of the currently selectedModCod, but may exceed the exit threshold configured for that ModCod,the terminal may continue to use the ModCod. In an alternate example,when the signal quality metric may drop below the entry threshold of thecurrently selected ModCod, and further drops below the exit thresholdconfigured for that ModCod, the ACM control module may determine thatModCod is no longer eligible for use. In this example, the ACM controlmodule may consider only more robust (and less efficient) ModCods forwhich the metric value may qualify.

In an example, the system/processor may downgrade the applied ModCod fora codeblock transmission by changing an encoding pattern of packets inthe codeblock when forward channel capacity is available so as tominimize the BER. For example, the gateway 130 may transmit data toterminal 110 using a forward link ACM ModCod that may be more robustthan requested by the terminal 110. This may be performed to maximizecapacity efficiency of a shared forward channel.

It should be appreciated that there may be several operating stateswithin the configured trajectory table 400. In some examples, theterminal 110A may drop down to a lower (less efficient/more robust)operating state, e.g., in the event the measured metric drops below theModCod exit threshold for that operating state. In this case, theterminal 110A may pick the trajectory table entry for which its measuredmetric is above the entry threshold. It should be appreciated that theterms “above” and “below,” as used herein, are relative terms. Forexample, in the event signal-to-noise ratio (SNR) is used, use of“above” and “below” may be proper. However, in the event BER metric isused, then use of “above” and “below” may be reversed or backwards. ForBER, for instance a higher bit error rate may be worse and a lower biterror rate may be better, which is the opposite for signal-to-noiseratio (SNR). In some examples, the terminal may move up to a higher(more efficient/less robust) operating state (e.g., the measured metricgoes above the ModCod entry threshold for a more efficient ModCod tableentry—the terminal may pick the best ModCod at which it qualifies). Insome examples, the terminal may also remain at its current operatingstate (e.g., previous ModCod) where neither of the above-mentionedcriteria are met.

FIG. 5 illustrates a block diagram showing downgrade in terminal ModCodfor enhancing efficiency on a shared forward channel, according to anexample. As depicted in FIG. 5 , an 800-byte data packet may be queuedin gateway forward transmit module to be sent to a terminal 2, followedby an 800-byte data packet to be sent to terminal 1. In this example, aterminal 2 may have requested ModCod as QPSK ½, and a terminal 1 mayhave requested ModCod 16APSK ⅔. Based on an assumption that a 16,000-bitcodeblock may be used for the forward channel, and that the 800-bytedata packet of terminal 2 contains 6,400 bits to be transmitted, at QPSK½, the terminal 2 data packet may occupy 12,800 bits of the 16,000 bitcodeblock (two coded bits per one data bit). This may lead to anavailability of 3,200 bits. In this specific example, the 800-byte datapacket of terminal 1 may as well contain 6,400 bits to be transmitted,but with a 16APSK ⅔ ModCod. The system may opt for one of the followingsolutions. As a solution, the system may leave the 3,200 available bitsin the QPSK ½ codeblock unoccupied, and may start a new 16APSK ⅔codeblock to hold the entire packet of terminal 1, wherein at ⅔ FEC the800-byte data packet of the terminal 1 may occupy 9,600 bits of the16,000 bit 16APSK ⅔ codeblock capacity. However, as an alternatesolution, and as shown in FIG. 5 , the system may segment the 800-bytedata packet of the terminal 1 such that 200 bytes (1600 bits) may becoded in the QPSK ½ (3,200 coded bits) to complete the QPSK ½ codeblock,while the second part or 600 bytes of data packet of the terminal 1 maybe coded in 16APSK ⅔ codeblock (7200 coded bits), leaving 8,800codeblock bits free for other data or control signaling. At therespective terminal 1, the two parts of the 800-byte data packet may bereassembled for processing. This solution is more efficient as itenables to fully utilize available codeblock space.

In an example, return link ACM operation of terminal (shown in FIG. 2 )may also be guided by a trajectory table. While the trajectory table forreturn link may be analogous to a forward trajectory table (as shown inFIG. 4 ) in some applications, there may be additional factors whichmight be considered in the ACM trajectory construction. For example, thefactors may include transmit power capability of the terminal radio,return channel symbol rate, and a target receive power level (at thegateway) for a given ModCod and symbol rate combination. The transmitpower capability of the terminal radio may enable to determine orconstrain symbol rates and/or ModCod combinations that the terminal maybe eligible to use such that the terminal may not transmit at a ratethat requires more than the maximum limit of radio power. In someexamples, a ranging process may be used during and/or after terminalcommissioning to establish this eligibility. The terminal may transmit asignal using a given ModCod at a given symbol rate and the gateway maymeasure and return a signal quality metric of the received signal to theterminal. Based on the signal quality metric, the terminal may adjusttransmit power to achieve a target receive signal quality metric valueat the gateway for corresponding return link. In some examples, whenmore than the available radio power may be required to reach a desiredtarget value, the combination of symbol rate and ModCod may not beeligible for the terminal to use. In some examples, when the terminalmay be eligible to use a given symbol rate and ModCod combination, theranging process may establish an initial transmit power setting for thatcombination from which open or closed loop transmit power controlalgorithms/technique for terminal return link may start upon applicationof the ModCod. Thus, the return link ACM trajectory table may beconstructed from a combination of configured target metric values andvalues derived from ranging. Several other methods may be used toconfigure or construct return link ACM trajectory table.

FIG. 6 illustrates an example of a configured trajectory table 600 for areturn link path of a terminal, according to an example. The table 600indicates application of the additional factors, as describedhereinabove and includes trajectory for each return link symbol ratesupported by the terminal 110. In an example, the return link ACMtrajectory table may be sorted by symbol rate, as might be applicable.For example, this may be applicable in examples wherein gateway 130 mayassign the symbol rate (based on prior terminal ranging results) and theterminal controls the corresponding ACM operation within the assignedrate. In an alternate example, the return link ACM trajectory table maybe sorted by relative efficiency or robustness across symbol rate andModCod combinations, using specific normalizing metric such as thresholdcarrier to noise ratio (C/No).

As shown in table 600, each entry may pertain to a given symbol rate 602and may include a ModCod format 604 indicating the modulation and codingto be applied. The table 600 may also include an eligibility 606 of aterminal to use the corresponding symbol rate and ModCod formatcombination. In an example, the eligibility may be derived by a rangingprocess, by configuration, or based on other aspects. For example, theother aspects may include a temporary disqualified state of a terminalfor a specific combination (symbol rate and ModCod format) that may haveled to a high error rate as per historical data. The table 600 mayinclude a minimum metric value (or threshold) 608 that may be requiredto be attained for a terminal to use the symbol rate and ModCod formatcombination. For example, the minimum metric value or threshold 608value may be SNR value or other such metrics. In some examples, when theterminal may not be able to maintain the minimum metric value orthreshold 608 at maximum transmit power, the ACM control module of theterminal may apply a more robust ModCod. The table 600 may include atarget metric value 610 to which the terminal uplink power control maycontrol transmit power. To enable this, the terminal may reduce transmitpower when it exceeds the target metric value 610, or may increasetransmit power when lesser than the target metric value 610, up to themaximum radio transmit power level. The return link based trajectorytable may not be limited to the mentioned aspects and may also includeother information, for example, a starting transmit power level for aranged and eligible ModCod for a given symbol rate. In some examples,the ACM control module may select the most efficient ModCod for a returnlink path for which the terminal may meet the minimum threshold value,and may use uplink power control feedback to attain the target value. Inan example, the terminal may continue to use a ModCod if above theminimum threshold, even if unable to reach the target value (due tobeing capped by maximum radio transmit power). In another example, ifthe terminal may be unable to attain the minimum threshold value for asymbol rate and ModCod combination when at maximum transmit power, theACM control module may apply more robust ModCod for which the minimumthreshold value may be attained. Several other aspects of ACMimplementation may be applicable.

The system and method described herein, may thus enable to executedifferent modes of ACM implementation, based on requirements/condition,as will be described further as different examples. It should beappreciated that although the below mentioned c/examples are explainedfor system including satellite networks, terminals and gateways,however, the implementation may also be applicable for wirelessterrestrial networks that use dynamic link adaptation, varyingmodulation or coding to optimize conditions and capacity for eachwireless terminal (for example, a smart phone). The modes ofimplementing ACM by the present system/method are discussed in detailherein and below in form of examples/scenarios.

Scenario 1: Differentiation of ACM Trajectory Tables Between OtherwiseSimilarly Provisioned Sites

In an example, the system and method described herein, may enable todifferentiate a terminal from a second terminal based on any or acombination of congestion parameters, and availability of a servicelevel defined for the respective terminals. Thus, the ACM optimizedtransmission may be performed on an individual terminal basis to thelink conditions being experienced by each given terminal. In someexamples, the trajectory table may facilitate guidance pertaining to theavailable transmission formats based on signal metrics reported by thereceiving side of the link signal. The conventional methods may rely onusing a common/similar trajectory table configuration for a similarterminal (modem, radio and antenna) configuration and expected satellitelink. However, as system operators may sell different grades of serviceavailability (referred herein as the “service level”) to differentcustomers, the use of a common/similar trajectory table may not beeffective.

For example, assuming similar link conditions (or weather conditions)for two terminals 1 and 2, the terminal site (for example, terminal 1)may be used by a user to support mission critical or high value publicsafety, government or enterprise traffic, and other such crucialbusinesses that may require high service availability, for example 99.9%corresponding to high service charges. In contrast to this, there may beother users/terminals (for example, the terminal 2) that may require alower service availability and also a lower service cost, such as, forexample, an Internet access home terminal user. To address such varyingdemand (service availability), the conventional techniques maydifferentiate service by providing higher cost equipment (largerantennas, more power radios), to high availability customers than tolower availability customers. However, the system and method describedherein, employ differentiated ACM trajectory tables to differentiateavailability, with or without implementation of differentiated equipmentconfigurations. This may facilitate to achieve varying serviceavailability (service level) for different type of terminals/users.

For example, in reference to FIG. 4 , for terminal (terminal 1), the ACMforward trajectory table may be configured such that that use ofModCod1, QPSK ¼, as well as ModCod 4, QPSK ½, and other more efficientModCods may be permitted. However, for the other terminal (terminal 2),the ACM forward trajectory table may be configured such that the use ofModCod1 is not permitted, but rather applies ModCod 4, QPSK ½, as itsmost robust (and least efficient) format. In an example, in case of rainattenuation at terminal 1, the corresponding ACM control module mayrequest gateway to apply ModCod 1, using 4 coded bits to deliver eachuser data bit on the forward channel. In this case, terminal 2 mayrequest no more than 2 coded bits to deliver each user data bit. In caseof rainy conditions (pertaining to terminal 1 a terminal 2), thecorresponding ACM control module of terminal 1 may enable use of twiceas much forward channel capacity to receive comparable traffic toterminal 2. In this case, the terminal 2 may lose service while theterminal 1 forward link may continue to operate, assuming equivalentrain conditions. It should be appreciated that various other factors maybe considered in differentiating ACM for various types of terminals.Further, differentiation may also be used for the return link trajectorytable in a similar manner as described for forward link trajectorytable. The differentiation for return link trajectory table may beaugmented or replaced with eligibility of high availability sites toutilize additional and limited lower symbol rate return capacity (forexample, symbol rate of 256 ksps). For example, link with symbol rate of256 ksps for high availability site may be maintained with greater rainattenuation than standard availability site (having 512 ksps link),given the same terminal radio power and antenna size.

Scenario 2: Adaptive Use of Different ACM Trajectory Tables at a GivenSite, Based on Various System Metrics and Controls

In an example, using the system and method described herein, an appliedModCod may be changed based on monitoring and periodic comparison ofshared forward channel aggregate utilization with a pre-definedthreshold. The change may include downgrading the ModCod when the sharedforward channel aggregate utilization is greater than the pre-definedthreshold. For example, a terminal (Term 1) may be configured with anACM forward trajectory table that enables a highly robust ModCod to berequested, for example, QPSK ¼. Another terminal (Term 2) may beconfigured with an ACM forward trajectory table that also enables QPSK ¼to be requested, but only while the shared forward channel aggregateutilization is below a given threshold, for example 85%. In thisexample, the Term 2 may obtain the utilization either by monitoring theforward channel or from system information that may broadcast on theforward channel from the gateway. In some examples, the monitoring maybe performed by counting symbols used for traffic versus null codeblocksor null-padding in codeblocks. In this example, the Term 1 may continueto be provided with the highest availability possible for its linkconditions, while the Term 2 may be provided with that same highestavailability during less congestion and with a standard availability induration of congestion.

It should be appreciated that this congestion-based differentiation mayalso be applied for the terminal return link (similar to the forwardlink). In examples pertaining to the return link, the Term2 may beconstrained to use some combinations depending on return bandwidthcapacity (in aggregate, or for a given symbol rate) as advertised by thegateway in an alternate example, the system and method described herein,may enable to differentiate service availability using differenttrajectory table configurations, which may be augmented by consideringcurrent system capacity utilization. The configuration of the trajectorytable may be altered based on capacity utilization and expectedcongestion during the day. In this example, specific ACM trajectorytable entries may be configured for use during pre-defined time of day,for example during typical off-peak periods. For example, the standardavailability for the Term 2 may be authorized to request QPSK ¼ on theforward channel only between 1 am and 8 am. Thus, availability (viacapacity efficiency) may be differentiated based on expected congestiontimes rather than on actual congestion status. The above mentionedprovisions may enable intermediate service availability (and servicecharges) in addition to high and standard service availability plans.

Scenario 3: Application of Different ACM Trajectory Tables for DifferentTraffic Classes

In some examples, the trajectory table may authorize use of given ModCodformat for a defined traffic class of service for the terminal. Thismeans that the configured ACM trajectory table may enable authorizedusage of a given ModCod format only for a given traffic class of servicefor the given terminal. For example, the defined traffic class mayenable to define high priority based services requiring high serviceavailability (such as mission critical traffic) such as, for exampleconversational voice, security monitoring, point-of-sale or order entrytransaction data at a business location. Other traffic class pertainingto inventory data uploads, training video downloads or guest Wi-FiInternet access service may be considered as lower-priority orlower-value traffic. For example, referring to example trajectory tables400 and 600 in FIGS. 4 and 6 respectively, certain ModCod entries may berestricted to defined traffic class of service i.e. services havinghigh-priority. Thus, only the high priority based services/traffic maybe eligible to use capacity less efficiently than low value traffic.Hence the lower value traffic may be dropped at the gateway or terminalprior to transmission.

It should be appreciated that the above mentioned examples of high andlow priority traffic may vary based on the terminal/userrequirements/preferences. In some examples, the defined traffic class ofservice may be determined by the terminal and/or gateway usingconventional configured multi-field classification rules, differentiatedservices code point (DSCP) values, or deep packet inspection techniques.In some examples, for a given terminal, the corresponding ACM controlfunction may indicate a different requested ModCod/ModCod format to thegateway for different traffic classes. The differentiated treatment oftraffic classes using ACM may be combined with adaptive use of differenttrajectory tables based on congestion or time of day. For example, auser such as an enterprise may be provided with high serviceavailability times for mission critical traffic, irrespective of channelcongestion. In this case, the trajectory table configuration mayindicate that mission critical traffic may be transported using a highlyrobust ACM ModCod when indicated by link conditions, for any channelloading level or time of day.

In some examples, the ACM trajectory table configuration may beconfigured to indicate that lower value traffic classes may be formattedusing a highly robust ACM ModCod if needed only during low congestionconditions (i.e., based on current channel loading or time of day), andnot during high congestion conditions. The configuration may indicate amore efficient ModCod as the lowest eligible for these traffic classesduring high congestion conditions. It should be appreciated that thetraffic class based differentiated ACM may be extended beyond the twotraffic groupings in the example described above (i.e., mission criticaland lower value) to more groups. For example, the traffic groupings mayinclude three groups including mission critical, high value and lowvalue, with different trajectory configurations settings for each group.

Scenario 4: Differentiation of Control Traffic ModCod Between Terminalson a Shared Forward Channel

In an example, a terminal may be operatively coupled to any of a gatewayand/or a second terminal to receive and/or transmit, on the appliedModCod, system control messages therefrom/thereto. In an example, theapplied ModCod may be modified based on the system control messages tobe transmitted/received and required availability of service. Forexample, the gateway may transmit specific system control messages toterminals on forward channels, in addition to user data traffic.

These control messages might be destined to specific terminals, togroups of terminals, or to all terminals. The system control messagesmay be selected from at least one of system access information, returnchannel information, return channel bandwidth allocation, terminalconfiguration profile, shared configuration profile, terminal softwareimage, handshake message, or diagnostic and status query. For example,the system access information may be addressed to all terminals and maypertain to at least one of system, satellite/carrier identification,timing, security key versions, or other associated aspects. The returnchannel information may pertain to return channel definitions, statusand/or controls. The return channel bandwidth allocation may be commonlyaddressed to all terminals, with each terminal parsing common messagesto find its own allocation. The terminal configuration profile, thehandshake message, and the diagnostic and status query may be addressedto specific terminals, whereas the shared configuration profile andterminal software image may be addressed to selective or all terminals.In some examples, when ACM is utilized for a shared forward channel, aModCod may be selected to convey such control messages. In an example,Table 1 depicts the possible categorization of specific controlinformation and corresponding ModCod that may be used.

TABLE 1 Control information type ModCod used System access informationHigh availability (e.g., QPSK ¼) Return channel definitions and Highavailability controls Return channel bandwidth allocations - Highavailability high availability terminals Return channel bandwidthallocations - Standard availability (e.g., standard availabilityterminals QPSK ½) Configuration messages, protocol High availability orstandard handshakes and diagnostic queries availability, depending onthe addressed to specific terminals specific terminal target serviceavailability Shared configuration profiles and High availability (achoice for terminal software images, addressed implementationsimplicity, to many or all terminals although differentiation by groupof terminal might be possible.

In some examples, the most robust (and least efficient) supported ModCodmay be used for this purpose, particularly for messages destined tomultiple terminals, so as to enable effective functioning of theterminal, which otherwise may be affected if specific control messagesare not received. However, the control messages may take a significantamount of shared forward channel capacity. To allow optimization of thecontrol channel capacity usage, the system and method described hereinmay send different shared control messages at different ModCods,depending on the terminal population intended to receive such messages.For example, in reference to table 400 (in FIG. 4 ), and assuming thatTerminal 1 may be authorized to request QPSK ¼, and Terminal 2 may notbe authorized to request QPSK ¼ but is authorized to use QPSK ½,specific information (control messages) may be destined to bothterminals to be sent at QPSK ¼. In some examples, specific informationmay be partitioned into two messages, for example, one message intendedfor Terminal 1 sent at QPSK ¼, and another message intended for Terminal2 sent at QPSK ½. In some examples, control messages that may berequired to be received by high availability terminals may be sent usingthe most robust ModCod for which those terminals are authorized to use.In this example, the control messages that need only be received bystandard availability terminals may be sent using the most robust ModCodfor which those terminals are authorized to use. In this example, thecontrol messages that are intended for both high and standardavailability terminals may be sent using high availability based mostrobust ModCod. In this manner, the respective service plan of anyterminal may be known to the gateway, or else may be understood based onACM signaling sent by the terminal ACM control module. The abovedescribed implementation may enable to control capacity to be optimizedwhile enabling sale of a higher availability differentiated grade ofservice.

Scenario 5: Automatic Manipulation of Forward Control Traffic ModCodBased on Utilization or Efficiency Thresholds

In case a single common target terminal service availability may bedesired, the conventional techniques may address by sizing equipment(gateway RFT, terminal antenna and power amplifier) to meet thatavailability on a probabilistic basis. However, it might be recognizedthat not all terminals receiving a shared forward channel may experiencethe same forward link conditions (as shown in FIG. 1B). Further, qualityof the forward link may also be based on position of the antennapertaining to a terminal. These variable conditions in a shared forwardchannel may not be possible to be considered based on conventionaltechniques. However, the system and method described herein mayfacilitate the gateway to dynamically change the control traffic ACMModCod based on forward channel utilization. This may be performed tooptimize traffic throughput capacity when congested, and to optimizeavailability when not congested. For example, in one situation, when aforward channel utilization may drop below a configured threshold value(for example 50%), the gateway may use a highly robust forward ACMModCod (such as QPSK ¼) for control traffic. In another situation, forexample, when the forward channel utilization may exceed a differentconfigured threshold value (for example 75%), the gateway may use a lessrobust forward ACM ModCod (such as QPSK ½) for control traffic. In someexamples, the terminals may be configured with a forward ACM trajectorytable containing both QPSK ¼ and QPSK ½, along with other more efficientModCod formats. The system and method described herein may alsoauthorize a terminal to request a ModCod number no lower than thecontrol message ModCod being received from the Gateway. For example, ifgateway uses QPSK ¼, terminals can request QPSK ¼, and if the Gatewayuses QPSK ½, terminals can request QPSK ½. This may lead to multipleadvantages such as, terminal with improper positioning of antenna mayreceive the service if the capacity is being wasted. This may ensurethat the system will not use inefficient coding when forward capacity iscongested. Another advantage may include effective service in conditionssuch as rain attenuation when forward capacity is available.Additionally, this may also enable to handle a startup scenario whenthere is absence of/less traffic in a link that is transmitted in rainyconditions, wherein the system may initially use QPSK ¼ because of low(i.e., zero) current channel utilization, such that the gateway permitsfaded terminals to receive service. The utilization of differentthreshold values may enable/disable use of the highly robust ModCod forshared forward control traffic. This may also ensure that the system maynot toggle back and forth due to the different overhead for controltraffic encoding. In an alternate example, the system may consider anaverage forward channel ModCod efficiency rather than the forwardchannel utilization, to determine whether to enable use of the highlyrobust ModCod for controlling traffic. For example, when most terminalssharing the forward channel may have changed to a robust ModCod such asQPSK ½, the system may assume that few terminals may have already fadedand might benefit from using QPSK ¼, assuming that most of the sharedforward channel is subjected to bad weather conditions/rain. In thiscase, the gateway may switch to QPSK ¼ for forward control traffic, withterminals requiring that ModCod being able to request it for forwarduser data traffic as well. It should be appreciated that the abovediscussed scenario may be based on assumption that the terminal may havesufficient return margin (for example, a powerful enough radioamplifier) to operate the return channel while the forward channelrequires robust ModCod such as QPSK ¼.

Scenario 6: Opportunistic Downgrade to a More Robust Forward ModCod whenCapacity is Available, to Minimize BER

In an example, wherein there may be insufficient queued traffic to filla codeblock using the requested ModCod for a forward traffic function,the system and method described herein may opportunistically downgradethe codeblock under construction to a more robust and less efficientModCod, provided the queued traffic may not exceed the codeblockcapacity. This operation may enable efficient capacity utilizationbecause it trades null padding of unused space in the codeblock for moreFEC coding of user traffic. This may provide higher coding protectionand therefore a lower average BER. Thus, the BER may be optimized evenbeyond the target BER average with no efficiency penalty. FIG. 7illustrates a block diagram of ModCod downgrade for an uncongestedforward channel, according to an example. As shown in 702 in FIG. 7 ,three 270 byte packets may be queued for transmission to terminal 1. Theterminal 1 may have requested a ModCod of 16APSK 9/10 (10 coded bitsused to deliver 9 data bits, modulated at 16APSK). Assuming, if thegateway encodes the terminal 1 queued data using 16APSK 9/10, the threequeued packets may occupy 7,200 bits of the 16,000 bit codeblock(assuming each 270-byte packet may take 2,400 bits) and the remaining8,800 bits may be null padded (and wasted). However, as shown in 704,the system and method described herein may use the opportunisticdowngrade concept, wherein the gateway may instead encode the packetsusing rate ½ FEC (for example, 16APSK ½). In this case, the three queuedpackets may occupy 12,960 bits of the 16,000 bit codeblock (assumingeach 270-byte packet may occupy 4,320 bits), and the remaining 3,040bits may be null padded (and wasted). Thus, as observed in this example,the same traffic may be delivered with more robust coding and lesswaste. It should be appreciated that an FEC rate downgrade may not belimited to these examples and other techniques pertaining toopportunistic downgrade may also be applicable. Further, it may befurther appreciated that the above mentioned concept may be applied to adedicated channel using ACM. This may include, for example apoint-to-point DVB-S2 TDM carrier to and/or from a terminal. In someexamples, if there may be an insufficient traffic queued to thedestination, the ModCod indicated by the trajectory table and currentlink quality metric may be downgraded to a more robust ModCod for agiven codeblock transmission. This may enable to optimize the error ratewith no capacity loss or traffic performance degradation. In someexamples, the system may avoid unnecessary return channel signaling torequest a ModCod change. For example, in a scenario in which a terminal1 may have requested the gateway to use ModCod 16APSK 9/10 for forwardtraffic. In times of low traffic, the system may opportunisticallydowngrade the delivery ModCod, for example to QPSK 9/10. In such cases,upon receiving QPSK 9/10 codeblocks, it may be undesirable for theterminal 1 to repeatedly request gateway to use 16APSK 9/10, therebywasting return channel capacity. To address this possible concern, thesystem and method may enable flagging an opportunistic ModCod downgradein some forward channel header. In an alternate solution, the system mayallow a terminal to repeat a ModCod request only after receiving someconfigured number of successive downgraded ModCod codeblocks. In someexamples, a satellite system operator may desire to allow only anaggregate forward channel capacity to an enterprise or virtual networkoperator (VNO) to be reserved for and shared by its collection ofterminals. In such examples, if capacity commitment may be expressed inunits of user traffic bits (or traffic plus terminal signaling bits),then the opportunistic ModCod downgrade may have no effect on the amountof traffic the user can send. However, if the capacity commitment isexpressed in units of symbols, then the opportunistic ModCod downgrademay cause more symbols to be occupied for the same amount of traffic, ormay cause the user traffic to be capped at a lower rate when the systemis uncongested. To address these concerns, the system may enable toaccount symbol usage for capacity contract fulfillment purposesaccording to the requested ModCods rather than the utilized ModCods.

Scenario 7: Opportunistic Downgrade to a More Robust TDMA Return ModCodwhen Capacity is Available, to Minimize BER

In an example, the system may downgrade time division multiple access(TDMA) return ModCod for a terminal when capacity is available so as tominimize the BER. The term TDMA channel may pertain to a sequence offrames, each of a fixed time duration. For example, a 45 millisecondreturn TDMA frame duration may be used in the IP over Satellite (IPoS)standard. Each TDMA frame may be further divided into a number of fixedsize time slots, for example, a frame may include 24 time slots. Thisreliance on time based sharing requires that terminals should be timesynchronized so that their transmissions do not overlap. This enablesmultiple terminals to transmit during different time slots of the sameframe. The gateway responsible to allocate TDMA return channel bandwidthmay commonly take account of the queued backlog for each terminal,either signaled in bandwidth requests on contention channels, orpiggybacked onto the data sent in using TDMA return channel allocation.Using the backlog information received from terminals sharing a givenreturn bandwidth pool, the gateway may allocate a number of transmitslots on a given return channel frequency to a given terminal. In anexample, when the system implements return channel ACM, with theterminal dynamically adapting its transmit modulation, coding, or bothbased on link quality metrics relayed from the gateway, the gatewaybandwidth allocation function may use the ModCod indication for eachgiven terminal to determine how many TDMA channel transmit slots toallocate to that terminal to match its backlog. In an example, when thesystem has more capacity available than the aggregate of terminalbacklog signaled, the gateway may commonly allocate extra bandwidth toeach or to many terminals, to be used opportunistically in eventadditional traffic is queued before the allocated transmit time arrives.Thus, a terminal might be allocated more return bandwidth than it hastraffic queued to send. The conventional solution may cause the terminalto null pad corresponding return transmission, and/or to transmit nullbursts, so that the gateway demodulator can remain locked to theinroute, so the system can differentiate between a lost burst and anunneeded return capacity allocation. However, the system and methoddescribed herein enable to opportunistically downgrade a given returnchannel transmission to a more robust ModCod when excess capacityallocation is available, similarly to the opportunistic forward ModCoddowngrade as has been described in the previous scenario. In particular,the ACM control module of the terminal may determine the optimal ModCodto be used for return channel transmission, independent of the volume ofdata queued and the amount of return capacity allocated. In this case,when an allocated transmission opportunity arrives, if the terminal hassufficient return traffic queued to fill the allocated capacity at theoptimal ModCod, the system may apply the optimal ModCod. However, if theterminal has received greater capacity allocation than the queued datamay occupy at the optimal ModCod, the terminal may opportunisticallydowngrade the transmit ModCod for the particular transmit opportunity,to the most robust ModCod format for which the queued traffic may fitinto the allocated number of time slots. This operation transportsreturn channel traffic more robustly without wasting capacity that couldotherwise be used, and without any degradation of the performance of thetransported traffic.

Scenario 8: Automatic Manipulation of ModCod for a Given MulticastStream Based on Capacity Threshold

In an example, the system may change the applied ModCod for a givenmulticast data delivery stream based on capacity threshold pertaining toutilization of bandwidth. Satellite systems may be suited to efficientlydeliver multicast traffic to many terminals, for services such as, forexample, video broadcast, distance learning, video conferencing, digitalsignage, and other applications. The system and method described hereinmay enable adaptive multicast delivery such that rather than configuringa minimum permitted ModCod for a given multicast stream,utilization/ModCod pairs may be configured. For example, for anuncongested forward channel, say below 50% utilization, a lowervalue/lower cost multicast stream may be permitted to adapt down to QPSK½. However, when utilization may exceed another threshold, for example70%, the same multicast stream may be constrained to avoid adaptingbelow 8PSK ½. Similarly, for another even higher threshold value, say85%, the same multicast stream may be constrained to avoid adaptingbelow 8PSK ⅔. This operation enables the system operator to enable aservice level that makes use of unused capacity without having low valuemulticast traffic be formatted with a ModCod that can excessivelydisplace other forward traffic.

FIG. 8 illustrates a block diagram of a computer system fordifferentiating application of ACM to enhance link performance,according to an example. The computer system 800 may be part of or anyone of the terminals 110, the gateway 130, the network data center 140,the network management system (NMS) 150, the business system 160, asshown in system 100-1 and/or 200 to perform the functions and featuresdescribed herein. The computer system 800 may include, among otherthings, an interconnect 810, a processor 812, a multimedia adapter 814,a network interface 816, a system memory 818, and a storage adapter 820.

The interconnect 810 may interconnect various subsystems, elements,and/or components of the computer system 800. As shown, the interconnect810 may be an abstraction that may represent any one or more separatephysical buses, point-to-point connections, or both, connected byappropriate bridges, adapters, or controllers. In some examples, theinterconnect 810 may include a system bus, a peripheral componentinterconnect (PCI) bus or PCI-Express bus, a HyperTransport or industrystandard architecture (ISA)) bus, a small computer system interface(SCSI) bus, a universal serial bus (USB), IIC (I2C) bus, or an Instituteof Electrical and Electronics Engineers (IEEE) standard 1394 bus, or“firewire,” or other similar interconnection element.

In some examples, the interconnect 810 may allow data communicationbetween the processor 812 and system memory 818, which may includeread-only memory (ROM) or flash memory (neither shown), and randomaccess memory (RAM) (not shown). It should be appreciated that the RAMmay be the main memory into which an operating system and variousapplication programs may be loaded. The ROM or flash memory may contain,among other code, the Basic Input-Output system (BIOS) which controlsbasic hardware operation such as the interaction with one or moreperipheral components.

The processor 812 may be the central processing unit (CPU) of thecomputing device and may control overall operation of the computingdevice. In some examples, the processor 812 may accomplish this byexecuting software or firmware stored in system memory 818 or other datavia the storage adapter 820. The processor 812 may be, or may include,one or more programmable general-purpose or special-purposemicroprocessors, digital signal processors (DSPs), programmablecontrollers, application specific integrated circuits (ASICs),programmable logic device (PLDs), trust platform modules (TPMs),field-programmable gate arrays (FPGAs), other processing circuits, or acombination of these and other devices.

The multimedia adapter 814 may connect to various multimedia elements orperipherals. These may include a devices associated with visual (e.g.,video card or display), audio (e.g., sound card or speakers), and/orvarious input/output interfaces (e.g., mouse, keyboard, touchscreen).

The network interface 816 may provide the computing device with anability to communicate with a variety of remove devices over a network(e.g., private network 170 or public network 180 of FIG. 1 ) and mayinclude, for example, an Ethernet adapter, a Fibre Channel adapter,and/or other wired- or wireless-enabled adapter. The network interface816 may provide a direct or indirect connection from one network elementto another, and facilitate communication and between various networkelements.

The storage adapter 820 may connect to a standard computer-readablemedium for storage and/or retrieval of information, such as a fixed diskdrive (internal or external).

Many other devices, components, elements, or subsystems (not shown) maybe connected in a similar manner to the interconnect 810 or via anetwork (e.g., private network 170 or public network 180 of FIG. 1 ).Conversely, all of the devices shown in FIG. 8 need not be present topractice the systems and methods described herein. The devices andsubsystems can be interconnected in different ways from that shown inFIG. 8 . Code or computer-readable instructions to implement the dynamicapproaches for payment gateway selection and payment transactionprocessing of the system 800 may be stored in computer-readable storagemedia such as one or more of system memory 818 or other storage. Code orcomputer-readable instructions to implement the dynamic approaches forpayment gateway selection and payment transaction processing of thesystem 800 may also be received via one or more interfaces and stored inmemory. The operating system provided on computer system 800 may beMS-DOS®, MS-WINDOWS®, OS/2®, OS X®, IOS®, ANDROID®, UNIX®, Linux®, oranother operating system.

As mentioned above, what is shown and described with respect to thesystems and methods above are illustrative. While examples describedherein are directed to configurations as shown, it should be appreciatedthat any of the components described or mentioned herein may be altered,changed, replaced, or modified, in size, shape, and numbers, ormaterial, depending on application or use case, and adjusted fordifferentiating application of ACM to enhance link performance insatellite communication systems.

It should be appreciated that the systems and methods described hereinmay facilitate to enhance link performance in satellite systems. Itshould also be appreciated that the systems and methods, as describedherein, may also include or communicate with other components not shown.For example, these may include external processors, counters, analyzers,computing devices, and other measuring devices or systems.

Moreover, single components may be provided as multiple components, andvice versa, to perform the functions and features described herein. Itshould be appreciated that the components of the system described hereinmay operate in partial or full capacity, or it may be removed entirely.It should also be appreciated that analytics and processing techniquesdescribed herein with respect to the optical measurements, for example,may also be performed partially or in full by other various componentsof the overall system.

It should be appreciated that data stores may also be provided to theapparatuses, systems, and methods described herein, and may includevolatile and/or nonvolatile data storage that may store data andsoftware or firmware including machine-readable instructions. Thesoftware or firmware may include subroutines or applications thatperform the functions of the measurement system and/or run one or moreapplication that utilize data from the measurement or othercommunicatively coupled system.

The various components, circuits, elements, components, and interfaces,may be any number of mechanical, electrical, hardware, network, orsoftware components, circuits, elements, and interfaces that serves tofacilitate communication, exchange, and analysis data between any numberof or combination of equipment, protocol layers, or applications. Forexample, the components described herein may each include a network orcommunication interface to communicate with other servers, devices,components or network elements via a network or other communicationprotocol.

Although examples are directed to satellite communication systems, suchas transponded satellite systems, it should be appreciated that thesystems and methods described herein may also be used in other varioussystems and other implementations. For example, these may include othervarious telecommunication test and measurement systems. In fact, theremay be numerous applications in cable or optical communication networks,not to mention fiber sensor systems that could employ the systems andmethods as well.

By leveraging existing customer terminals, the system and methodsdescribed herein may provide efficient processing techniques and acost-effective approach that may be readily integrated into various andexisting network equipment. The systems and methods described herein mayprovide mechanical simplicity and adaptability to small or largesatellite communication systems. Ultimately, the systems and methodsdescribed herein may increase efficiency, reduce cost, maximize existingequipment, minimize adverse effects of traditional systems, and improvelink performance.

What has been described and illustrated herein are examples of thesystems and methods along with some variations. The terms, descriptions,and figures used herein are set forth by way of illustration only andare not meant as limitations. Many variations are possible within thescope of the systems and methods described herein, which are intended tobe defined by the following claims—and their equivalents—in which allterms are meant in their broadest reasonable sense unless otherwiseindicated.

1. A system comprising: a processor; and a memory operatively coupledwith the processor and comprising a set of instructions, which whenexecuted, cause the processor to: dynamically compute bandwidth capacityof a terminal from a plurality of terminals; and automaticallydetermine, based on the computed bandwidth capacity of the terminal andusing an Adaptive Coding and Modulation (ACM) to technique, a Modulationand Coding combination (ModCod) to be applied for transmission to orfrom the terminal to optimize bit error rate (BER) performance.
 2. Thesystem of claim 1, wherein the processor, for the plurality ofterminals, dynamically determines aggregate bandwidth availability andcongestion within the ACM technique to optimize sharing of availablebandwidth.
 3. The system of claim 1, wherein the system is a dynamiclink adaptation system.
 4. The system of claim 1, wherein the ACMtechnique uses a trajectory table to adaptively change or allowpermission for use of the applied ModCod by the terminal.
 5. The systemof claim 4, wherein configuration of the trajectory table is alteredbased on at least one of capacity utilization or expected congestionduring the day.
 6. The system of claim 4, wherein the trajectory tableauthorizes use of a given ModCod format for a defined traffic class ofservice for the terminal.
 7. The system of claim 1, wherein the appliedModCod is changed for the terminal based on any or a combination ofparameters associated with at least one of satellite link, congestion,weather, availability of a service level to be provided to the terminal,terminal radio power, or antenna size.
 8. The system of claim 1, whereinthe applied ModCod is changed based on monitoring and periodiccomparison of shared forward channel aggregate utilization with apre-defined threshold, wherein the change comprises to downgrading theModCod when the shared forward channel aggregate utilization is lessthan the pre-defined threshold.
 9. The system of claim 1, wherein theterminal is differentiated from a second terminal based on any or acombination of congestion parameters, and availability of a servicelevel defined for the respective terminals.
 10. The system of claim 1,wherein the terminal is operatively coupled to any of a gateway or asecond terminal to receive or transmit, on the applied ModCod, systemcontrol messages therefrom/thereto, wherein the system control messagesare selected from at least one of system access information, returnchannel information, return channel bandwidth allocation, terminalconfiguration profile, shared configuration profile, terminal softwareimage, handshake message, or diagnostic and status query, and whereinthe applied ModCod is modified based on the system control messages tobe transmitted/received and required availability of service.
 11. Thesystem of claim 10, wherein the gateway dynamically changes ModCod fortransmitting control traffic based on forward channel utilization tooptimize traffic throughput capacity when congested, and to optimizeavailability when not congested.
 12. The system of claim 1, wherein thesystem, for a codeblock transmission, downgrades the applied ModCod bychanging an encoding pattern of packets in the codeblock when forwardchannel capacity is available so as to minimize the BER to optimize theBER performance.
 13. The system of claim 1, wherein the system isimplemented in a gateway device.
 14. The system of claim 1, wherein thesystem downgrades TDMA return ModCod for the terminal when capacity isavailable so as to minimize the BER to optimize the BER performance, thedowngrading being performed based on at least one of a number of TDMAchannel transmit slots to allocated, a backlog at is the terminal, or amost robust ModCod that conveys the backlog in that number of slots. 15.The system of claim 1, wherein the system changes the applied ModCod fora given multicast data delivery stream based on capacity thresholdpertaining to utilization of bandwidth.
 16. A method comprising:dynamically computing, at a network device, bandwidth capacity of aterminal from a plurality of terminals; and automatically determining,at the network device, based on the computed bandwidth capacity of theterminal and using an Adaptive Coding and Modulation (ACM) technique,Modulation and Coding combination (ModCod) to be applied fortransmission to or from the terminal to enable optimized bit error rate(BER) performance.
 17. The method of claim 16, wherein the networkdevice is a gateway.
 18. The method of claim 16, wherein the networkdevice, for the plurality of terminals, dynamically determines aggregatebandwidth availability and congestion within the ACM technique tooptimize sharing of available bandwidth.
 19. The method of claim 16,wherein the ACM technique uses a trajectory table to adaptively changeor allow permission for use of the applied ModCod by the terminal.
 20. Anon-transitory computer-readable storage medium having an executablestored thereon, which when executed instructs a processor to perform amethod as follows: dynamically computing, at a network device, bandwidthcapacity of a terminal from a plurality of terminals; and automaticallydetermining, at the network device, based on the computed bandwidthcapacity of the terminal and using an Adaptive Coding and Modulation(ACM) technique, Modulation and Coding combination (ModCod) to beapplied for transmission to or from the terminal to optimize bit errorrate (BER) performance.